A conventional gas-fired water heater may be operated to heat water by igniting natural gas or liquid petroleum gas from a gas supply system or cylinders, which is started by opening a water valve of a water pipe passing through the heater. If the gas-fired water heater or geyser is improperly installed such as installed in an interior of a house, the gas may be burned incompletely due to a limited oxygen supply in an interior especially in a closed interior in a cold weather season to produce poisonous carbon monoxide which may cause suffocation or even death to someone taking a bath or living in a closed room when exposed under the carbon monoxide gas.
It is therefore expected to provide an oxygen supply system in addition to the geyser.